first of all, if two parts are fixed relative to each other, and if they have the same material property (e.g. coeff. of friction), then group them! On the other hand, if two parts are fixed relative to each other, but do not have the same material property, then place a force sensor between then: attach a force sensor to the first shape, then attach the second shape to the force sensor. This can also be used if you need to measure the force/torque on the sensor.

If two shapes are attached via a force sensor, then make sure that they do not overlap (or at least do have exclusive local respondable masks), otherwise they will start to shake because of the contradictory constraints.

first of all, if two parts are fixed relative to each other, and if they have the same material property (e.g. coeff. of friction), then group them! On the other hand, if two parts are fixed relative to each other, but do not have the same material property, then place a force sensor between then: attach a force sensor to the first shape, then attach the second shape to the force sensor. This can also be used if you need to measure the force/torque on the sensor.

If two shapes are attached via a force sensor, then make sure that they do not overlap (or at least do have exclusive local respondable masks), otherwise they will start to shake because of the contradictory constraints.

Hi，Do you mean I can just attach two objects by add a force sensor, and then just attach a force sensor to the first shape, then attach the second shape to the force sensor as you said? I tried several times, the force sensor still remain at its original location, and when simulate, objects linked by force sensors disintegrated, however icon showed the force sensor was dynamically enabled, as you can see in the following picture.

I failed to find more information about add & attach force sensors in manual, sorry to bother you again.

It seems you are having another problem in your scene, since your force/torque sensor appears to come apart (break apart). This usually happens if you have large mass or inertia ratios. Check the design considerations 7 and 8 here.

I would put the force/torque sensor close to the point where the two shapes connect. For some physics engines the position of the connection makes a difference, for others it doesn't. Of course if at some point later you want to read-out the force/torque values of the sensor, the location of the force/torque sensor is very inportant (less if you just need to rigidly connect two shapes).

Adjusting the masses and inertias is with Bullet and ODE can be a guessing and trial-and-error game. With Vortex (and to a certain extent Newton), it is much less, since two two engines behave much better with realistic values (i.e. values taken from the real robot for instance).